1. Field of the Invention
The present invention relates to a clamp. More particularly, the present invention relates to a clamp for screen printing. The clamp increases the service life of screen printing equipment.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Screen printing is a technique in the field of art involving ink pressed through a mesh screen onto a substrate, such as a canvas or a t-shirt. The mesh is usually woven and treated with an ink-blocking stencil so that the ink only passes through selected portions of the screen. The ink forms a pattern on the substrate as a roller, squeegee, or other scraping means pushes the ink across the screen. Screen printing is also known as silkscreen or seriography.
The screen includes porous woven fabric or mesh extended or a frame piece. The mesh can be made of manufactured materials, such as nylon and polyester or organic materials, such as silk. The frame is comprised of wood, metal, or other suitable material. The pattern on the screen is created by non-permeable material covering areas of the screen, similar to a stencil. The uncovered areas of the screen show the pattern, while the covered areas form a negative image of the pattern. The ink presses through these uncovered areas. There are known treatments for heat or light treatment of the screen with the stencil.
The ink pattern is applied to a substrate underneath the screen. As the ink is loaded onto one edge of the screen, a floodbar or scraping means moves the ink evenly across the screen so that the ink falls through the holes in the mesh only in the selected open areas of the screen. As such, the ink pattern is applied to the substrate by the slight downward force of the scraping action. Other slight variations in the process are possible, including separating the steps of filling the open areas of the mesh and contacting the substrate. In that variation, a roller or squeegee applies the downward force from mesh to substrate separate from the ink application. Multi-color patterns are possible with variations in the mesh for each color and allowing a drying time between ink applications.
The working life of a patterned screen can increase if used for more than one pattern. The coated material can be removed from the mesh with chemical treatment by liquids, gels, or powders. The screen must be thoroughly cleaned before re-use with a new pattern of coated material.
Importantly, it is common to use a coated screen multiple times. It is unlikely that there will only be a single substrate for ink application, especially considering the amount of work and effort required for the patterned coating process for the screen. The types of substrates can vary, and the screen can apply the ink pattern on a wide variety of objects, including caps, balloons, stickers, posters, etc. The number of substrates can also vary, such as several hundred t-shirts or several thousand t-shirts. In order to insure consistent placement on multiple repeated substrates, the current technology has developed a platen to be used in conjunction with the screen. The platen is a mounting board for positioning the substrate. The platen and screen engage each other so that the relative position of the platen to the screen can be maintained each time the platen and screen are connected. In this manner, consistent mounting of the substrate on the platen and consistent positioning of the platen relative to the screen insures consistent application of the ink pattern on the same location on the substrate. Various means have been used to consistently position the platen relative to the screen, including clamps attached to the screen and alignment pins. The platen technology is especially important for using multiple color applications on the same substrate. New techniques and tools for consistent ink application on each substrate continue to be developed.
In the past, various patents have issued relating to devices to consistently position the platen relative to the screen in screen printing. For example, U.S. Pat. No. 3,222,055, issued to Cook on Dec. 7, 1965 discloses clamps with dual threaded jaws. The jaw elements are connected by screw threads that adjust the distance between the jaws for clamping. The invention shows the flush contact of the jaws on the item to be clamped.
U.S. Pat. No. 4,962,918, issued to Yang on Oct. 16, 1990 teaches a clamping set having double-coordinate clamping function and being extensible for adjusting clamp depth. The clamping action occurs in more than one dimension, wherein a sliding member engages the C-clamp portion of the device. The threaded screw on the sliding member can be set perpendicular to the clamp.
U.S. Pat. No. 4,938,130, issued to Thorpe on Jul. 3, 1990, describes a screen printing registration device and registration method. The '130 patent addresses the exact problem of consistent alignment of the platen and frame for multiple applications or re-applications. The clamp of the invention uses a pin on the platen to insure alignment of every clamped frame.
U.S. Pat. No. 2,642,905, issued to Hewat on Jun. 23, 1953, shows a work holding clamp with an angularly adjustable pressure element. This clamp features the usual elements, such as vertical screw threads and a clamping surface, but it also has spaces for other screws to engage the clamp at adjustable angles. This is useful for irregularly shaped projects, or ones where the project may be worked on after being positioned into the clamp.
U.S. Pat. No. 4,949,635, issued to Padula on Aug. 21, 1990, discloses a textile printing apparatus for multicolor printing. It contains a plurality of upper and lower arms radiating from a central hub and axle and which are rotatable with respect to one another. The lower arms have platforms for receiving textile workpieces, and the upper arms have clamping means for holding a stencil on top of a workpiece.
holder.
It is an object of the present invention to provide a clamp means for identical placement of platens relative to a frame during the screen printing process.
It is another object of the present invention to provide a clamp means, which increases the working life of the framed screen of the screen printing process.
It is an object of the present invention to provide a clamp means removably attached to the frame of a screen of the screen printing process.
It is another object of the present invention to provide a clamp means friction fit onto the frame of a screen of the screen printing process.
It is another object of the present invention to provide a clamp system, which maintains clamping force with reduced risk of mechanical failure.
It is an object of the present invention to provide a clamp system with reduced risk of damage to the frame of the screen.
It is still another object of the present invention to provide a clamp means with an adjustable alignment pin.
It is another object of the present invention to provide an adjustable alignment pin parallel to the jaw members of the clamp system.
It is still another object of the present invention to provide an adjustable alignment pin with improved resistance to deformations and/or buckling.
It is an object of the present invention to provide a clamp system, which is easier and lighter to transport and carry.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and claims.